Buyers throughout Britain typically spend pounds 25.40 every month on a mortgage out of every pounds 100 they take home, according to the TSB's Affordability Index.
That figure is based on data for the second quarter of the year, and compares with pounds 30.90 for the corresponding three-month period last year, representing a drop of 18 per cent.
TSB, which believes homes have not been so affordable since 1978, reckons the cost of servicing a mortgage will fall to its lowest level by Christmas when homeowners will spend an estimated pounds 25.20 on their loans.
But a probable 1 per cent interest rate increase and gradually rising house prices could see that figure rise to pounds 29.10 by the end of next year.
TSB's mortgage marketing manager Steve Lowe said: "This is excellent news for would-be housebuyers planning to move in the next few months. And it could even act as a trigger for those people considering a move in the near future."
John Stewart, an independent housing analyst who compiles the TSB Index, said: "The combination of April's tax cuts, lower mortgage rates and faster average earnings growth have helped improve affordability over the past few months. These factors have been more than enough to outweigh the negative impact of a slight increase in house prices.
"And we're likely to enjoy the benefits in terms of affordability until at least the end of the year."